Plasma CVD method and apparatus

ABSTRACT

The present invention provides a plasma CVD method for forming a plasma from a deposition material gas by application of an electric power, and thereby forming a film on a deposition target object in the plasma, wherein the formation of the plasma from the material gas is performed by applying an RF power and a DC power, and the DC power is applied to an electrode carrying the deposition target object. The present invention also provides a plasma CVD apparatus for forming a plasma from a deposition material gas by applying an electric power from the power applying means, and thereby forming a film on a deposition target object by exposing the deposition target object to the plasma, wherein the power applying means includes RF power applying means and DC power applying means, and the DC power applying means applies an electric power to the electrode carrying the deposition target object.

TECHNICAL FIELD

The present invention relates to plasma CVD method and apparatus forforming a film on a substrate to be deposited, i.e., a deposition targetobject by forming a plasma from a deposition material gas and byexposing the object to the plasma.

BACKGROUND ART

A plasma CVD method has been widely used for manufacturing various kindsof semiconductor devices such as ICs and sensors utilizingsemiconductors, manufacturing various kinds of thin-film devices used insolar cells and LCDs (liquid crystal displays), forming films having ahigh wear resistance on mechanical parts and tools requiring a high wearresistance, and others. Various apparatuses for implementing the plasmaCVD method have been known, and a plasma CVD apparatus of a capacitycoupling type shown in FIG. 8 is an example of such an apparatus.

The apparatus shown in FIG. 8 is known as a parallel-plated plasma CVDapparatus, and has a vacuum container 1 used as a deposition chamber, inwhich an electrode 2 also serving as an object holder for carrying asubstrate S, i.e., a deposition target object S as well as an electrode3 opposed to the electrode 2 are arranged.

The electrode 2 is usually used as a ground electrode, and isadditionally provided with a heater 21 for heating the object S mountedthereon to a deposition temperature. When the object S is heated by aradiation heat, the heater 21 is separated from the electrode 2.

The electrode 3 is an electric power applying electrode for applying anelectric power to a deposition material gas, which is introduced betweenthe electrodes 2 and 3, for forming a plasma. In the illustratedexample, the electrode 3 is connected to an RF (radio-frequency) powersource 32 via a matching box 31.

The vacuum container 1 is connected via piping to an exhaust device 5,and is also connected via a piping to a gas supply unit 4 of thedeposition material gas. The gas supply unit 4 includes one or more gassources 431, 432, . . . for supplying deposition material gasesconnected to mass flow controllers 411, 412, . . . and valves 421, 422,. . . .

According to this parallel-plated plasma CVD apparatus, the depositiontarget object S is transported into the vacuum container 1 by anunillustrated object transporting device, and is mounted on theelectrode 2. The exhaust device 5 operates to achieve a predetermineddegree of vacuum in the container 1, and the gas supply unit 4 suppliesthe deposition material gas into the container 1. The RF electrode 3 issupplied with an RF power from the power source 32, and thereby theplasma is produced from the introduced gas. A film is deposited on thesurface of the object S in the plasma thus produced.

A plasma CVD apparatus of an induction coupling type shown in FIG. 9 hasalso been used. This apparatus differs from the apparatus in FIG. 8 inthat the object holder 2 is electrically floated, the electrode 3 inFIG. 8 is replaced with an induction coil electrode 7 wound around thecontainer 1, and the matching box 31 and the RF power source 32 areconnected to the opposite ends of the induction coil 7. Structures otherthan the above are the same as those of the apparatus in FIG. 8, and thesame or similar parts and portions bear the same reference numbers.

A plasma CVD apparatus shown in FIG. 10 has also been used for forminghigh adherence films for engineering purposes and other films. Theapparatus in FIG. 10 differs from the apparatus in FIG. 8 in that theelectrode 2 also serving as the object holder is used as the powerapplying electrode for applying the electric power, and the electrode 3opposed to the electrode 2 is used as the ground electrode. In theillustrated example, the electrode 2 is connected to the RF power source32 via the matching box 31. Structures other than the above are the sameas those of the apparatus in FIG. 8, and the same or similar parts andportions bear the same reference numbers.

In this apparatus, ionized particles in the plasma apply an impactagainst the object S carried by the power applying electrode 2.Therefore, this apparatus can be suitably used for manufacturing tools,machine parts and others. In the apparatus shown in FIG. 8, ionizedparticles apply a less impact against the object S, so that thedeposition target object S can be selected from a wider range.

In the apparatus in FIG. 10, a self-bias voltage appears on the RFelectrode 2, and affects the quality of the deposited film. Generally,the deposition under the conditions of such a large self-bias voltagecan achieve effects such as improvement of a deposition rate andimprovement of a film hardness, although the latter depends on a kind ofthe film.

A plasma CVD apparatus shown in FIG. 11 is also available. Thisapparatus differs from the apparatus in FIG. 8 in that an RF powergenerating device 33 is employed instead of the RF power source 32, andis connected to the electrode 3 via the matching box 31. The RF powergenerating device 33 includes an RF power amplifier 34 and an RFarbitrary waveform generating device 35 connected thereto. Structuresother than the above are the same as those of the apparatus in FIG. 8,and the same or similar parts and portions bear the same referencenumbers.

According to this apparatus, formation of the plasma from the depositionmaterial gas is performed by applying an RF power, on which pulsemodulation or another modulation is effected, from the RF powergenerating device 33 to the electrode 3.

Although not shown, such plasma CVD apparatuses are also known thatdiffer from the parallel-plated plasma CVD apparatuses in FIGS. 8 and10, respectively, in that the matching box 31 and the RF power source 32in FIGS. 8 and 10 are replaced with a DC power source capable of turningon/off a current. According to these apparatuses, formation of theplasma from the deposition material gas is performed by applying the DCpower in a pulse form.

Although not shown, such a method has already been known that forms aplasma from the deposition material gas by applying a modulated RF powerby using the induction coupling type-plasma CVD apparatus in FIG. 9provided with RF power generating device 33 shown in FIG. 11 instead ofthe RF power source 32.

Various kinds of films can be formed by the plasma CVD apparatuses inthe prior art already described. For example, the pressure in the vacuumcontainer 1 is set to about several hundreds of millitorrs, and thedeposition material gas supply unit 4 supplies a carbon compound gassuch as a methane (CH₄) gas or an ethane (C₂H₆) gas, or a mixture ofsuch a carbon compound gas and a hydrogen (H₂) gas, whereby a carbon (C)film is formed on the deposition target object S.

In this case, the film quality can be controlled by changing theprocessing temperature of the deposition target object S. For depositinga film on an object made of, e.g., a synthetic resin such as polyimide,the deposition temperature is set to about 100° C. or less in view ofthe heat resistance of the object, in which case a diamond-like carbon(DLC) film is deposited. Since this DLC film has a large hardness, it isutilized as diaphragms of loud speakers and coatings of ornaments.

With increase in deposition target object temperature, the carbon filmhas a larger hardness. Therefore, in the case where carbon films areused as coatings for improving, e.g., a surface hardness of cuttingtools, various kinds of machine parts or the like, the depositiontemperature is generally set to 500° C. or more. If the depositiontemperature is set to 900° C. or more, a diamond film is deposited.

As already described, however, the plasma CVD methods and apparatuses,which produce the plasma from the material gas by applying thereto thesteady or modulated RF power or by applying the steady or pulse-form DC.power, cannot perform the film deposition at a sufficiently lowtemperature, and the deposited film cannot have a sufficiently largeadherence to the object.

Particularly, in the case where a hard carbon film such as a DLC. filmis formed by the plasma CVD method and apparatus, an internal stress isliable to occur in such a hard film due to expansion and contraction ofthe film itself or the like, and therefore an adjustment with respect tothe surface to be deposited may be deteriorated, which tends to causepartial separation or peeling. In order to improve the film adherence,the deposition may be performed under the condition that the self-biasis large. However, this further increases the hardness of the depositedfilm, which reduces the film adherence.

Accordingly, a first object of the present invention is to provideplasma CVD method and apparatus for depositing a film on a depositiontarget substrate, i.e., deposition target object in a plasma produced byapplying an electric power to a deposition material gas, andparticularly plasma CVD method and apparatus which can form a filmhaving a good adherence to the object.

A second object of the present invention is to provide plasma CVD methodand apparatus for depositing a film on a deposition target substrate,i.e., deposition target object in a plasma produced by applying anelectric power to a deposition material gas, and particularly plasma CVDmethod and apparatus which can perform film deposition at a lowertemperature than the method and apparatus in the prior art.

A third object of the present invention is to provide plasma CVD methodand apparatus for depositing a film on a deposition target substrate,i.e., deposition target object in a plasma produced by applying anelectric power to a deposition material gas, and particularly plasma CVDmethod and apparatus which can form a carbon film having a high hardnessand a good adherence to the object.

DISCLOSURE OF THE INVENTION

For achieving the first object, the present invention provides a plasmaCVD method for forming a plasma from a deposition material gas byapplying an electric power, and forming a film on a deposition targetobject, i.e., deposition target substrate in the plasma, wherein theformation of the plasma from said material gas is performed by applyingan RF power and a DC. power, and the DC. power is applied to anelectrode carrying the deposition target object.

For achieving the first object, the invention provides a plasma CVDapparatus for forming a plasma from a deposition material gas suppliedfrom a deposition material gas supply unit by applying an electric powerfrom power applying means, and exposing a deposition target substrate,i.e., a deposition target object to the plasma for forming a film on theobject, wherein said power applying means includes RF power applyingmeans and DC. power applying means, and said DC power applying meansapplies the power to an electrode carrying the deposition target object.

According to the plasma CVD method and apparatus of the invention, theplasma is formed from the deposition material gas while applying the DC.power to the electrode carrying the deposition target object, so thationized particles in the plasma are accelerated toward the depositiontarget object, and the accelerated particles produces a cleaning effectto remove contaminants or the like sticking to the surface of the objectwhile the deposition is being performed. In addition to this cleaningeffect, ionized particles contributing to the deposition are implantedinto a surface portion of the object to form a inclination compositionlayer, so that a film having a good adherence to the object can beformed.

According to the method and apparatus of the invention, since theionized particles applies an impact on the deposition target object, themethod and apparatus of the invention which can be used formanufacturing devices such as ICs can be used more suitably inmanufacturing of tools and machine parts.

The other electrode opposed to the electrode carrying the depositiontarget object may be disposed in a container for deposition, andtherefore may be an electrode corresponding to the electrode 3 opposedto the electrode 2 serving as the object holder in the parallel-platedplasma CVD apparatus shown in FIGS. 8, 10 and 11. Alternatively, theother electrode may be an induction coil electrode wound around thecontainer, and therefore may be an electrode corresponding to the coilelectrode 7 in the induction coupling type plasma CVD apparatus shown inFIG. 9.

In the method and apparatus of the invention, said RF power may be amodulated RF power. The modulation may be pulse modulation performed byon/off of power application or pulse-like modulation , and may bebroadly an amplitude modulation.

A plasma of a high density can be produced owing to this modulation,which is effected on the RF power for plasma production from thedeposition material gas, so that a reactivity is improved, and thereforedeposition at a low temperature is allowed. Owing to the abovemodulation, the temperature of electrons and ions in the plasma iscontrolled to increase relatively the amount of produced radicals in theplasma which contribute to the deposition. This promotes reaction at thesurface of the deposition target object, and therefore improves the filmadherence and deposition rate. According to the method and apparatus ofthe invention, the foregoing second object can be achieved by employingthe modulated RF power as the foregoing RF power.

According to the method and apparatus of the invention, a basic RF powerbefore modulation may have, for example, a sinusoidal, square,saw-tooth-like or triangular waveform.

The basic RF power before modulation may have a predetermined frequency(e.g., 13.56 MHz) between about 10 MHz and about 100 MHZ, and a pulsemodulation is effected on the basic RF power with a modulation frequencybetween about 1/10⁵ and about 1/10 of the predetermined frequency, andmore preferably between about 1/10⁴ and about 1/10³. In other words, thepulse-modulated RF power may be produced by affecting the pulsemodulation on the basic RF power having the frequency in the above rangewith the modulation frequency between about 100 Hz and about 10 MHZ, andmore preferably between about 1 kHz and about 100 kHz.

For deposition of a carbon (C) film which will be described later, thepulse modulation may be effected on the basic RF power of a frequencyof, e.g., 13.56 MHz with the modulation frequency from about 100 Hz toabout 500 kHz. In particular, for forming highly crosslinked carbonfilm, the modulation frequency from about 100 Hz to about 5 kHz isdesirably employed. For depositing a high-density carbon film, themodulation frequency from about 10 kHz to about 100 kHz is desirablyemployed.

The reason for employing the basic RF power of the frequency in theabove range is as follows. If it were lower than 10 MHz, the plasmadensity would be insufficient. Even if it were higher than 100 MHZ, theplasma density would not be improved further, and an electric power costwould uselessly increase. The reason for employing the pulse modulationfrequency in the above range is as follows. If it were lower than 100Hz, the modulation would not provide an effect of improving the plasmadensity. Even if it were higher than 10 MHz, the plasma density wouldnot be improved further, and an electric power cost would uselesslyincrease.

The duty ratio (on-time/(on-time+off-time)) of the pulse modulation maybe from about 10% to about 90%. Although not restricted, it may betypically about 50%. If it were lower than 10%, the reaction time wouldbe short and therefore the deposition rate would lower. If it werehigher than 90%, a time for power application would be excessively long,and therefore an effect of improving the plasma density by the modulatedRF power would be reduced.

In the method and apparatus of the invention, the DC potential appliedto the electrode carrying the deposition target object is usuallynegative potential. The negative potential during deposition have amagnitude, which does not cause or substantially cause etching of thedeposition target object and/or the film formed thereon by ionizedparticles which are accelerated.

According to the method and apparatus of the invention, the RF power maybe applied to the electrode carrying the deposition target object, inwhich case an RF power and a DC. power are applied together in asuperposed manner. Alternatively, the RF power may be applied to theelectrode opposed to the electrode carrying deposition target object.

In the case where the RF power is applied to the electrode carrying thedeposition target object, ionized particles exert a large impact to thedeposition target object. Therefore, the electrode supplied with the RFpower may be selected depending on a material, purpose and others of thedeposition target object.

According to the method and apparatus of the invention, the DC. powermay be in a pulse form, which further improves a density of the plasmaproduced by electric discharging. Also, the effect of accelerating theionized particles in the plasma toward the deposition target object maybe the same or improved, because the ionized particles are particularlystrongly accelerated during turn-on of the DC. power.

The frequency of the pulse modulation may be in a range from about 1 kHzto about 100 kHz, because the frequency lower than 1 kHz would notimprove the effect of improving the plasma density, and the frequencyhigher than 100 kHz would uselessly increase the cost without furtherimproving the effect of improving the plasma density. The duty ratio maybe in a range from about 10% to about 90%, and is typically about 50%,although not restricted thereto.

In the method for forming the plasma from the deposition material gas byapplying the electric power, and forming the film on the depositiontarget object under the plasma, an interface layer may be formed on theobject, and thereafter an upper layer of the same material as theinterface layer may be formed, in which case formation of the interfacelayer is performed by the foregoing method of the invention, and theinterface layer thus formed can have a good adherence to the depositiontarget object.

The power applied for formation of the upper layer is not restricted,and the interface and upper layers are made of the same material andthus have good adjustment properties, so that a good adherence can beachieved between them. In addition to the interface layer, the upperlayer may also be formed by the foregoing method of the invention, inwhich case the adherence between them can be further improved.

The method and apparatus of the invention described above may beprovided with a deposition material gas supply un it which can supply,as the deposition material gas, a gas of carbon compound for forming acarbon film, or can supply a gas of a carbon compound together with agas of a kind different from the carbon compound gas for forming thecarbon film. By using such deposition material gas, the carbon film, andtypically a DLC. film may be formed on the deposition target object.

In this case, since the plasma is formed from the deposition materialgas while applying the DC. power to the electrode carrying thedeposition target object, a carbon film having a large hardness and agood adherence may be formed on the object for the same reason as theabove. Thus, this can achieve the third object of the invention.

Carbon compound for the carbon film deposition may be one or morematerial selected from a group including methane (CH₄), ethane (C₂H₆),propane (C₃H₈), butane (C₄H₁₀), acetylene (C₂H₂), benzene (C₆H₆), carbontetrachloride (CF₄) and carbon hexafluoride (C₂F₆) which have beengenerally used for carbon film deposition. Each of these materials maybe solely used, or may be used together with another kind of gas such asa hydrogen (H₂) gas or an inert gas for the carbon film deposition.

For forming the carbon film by the method and apparatus of theinvention, there may be employed a deposition material gas supply unitwhich can supply, in addition to the deposition material gas for thecarbon film deposition, either or both of a nitrogen (N₂) gas or anammonia (NH₃) gas, whereby either or both the nitrogen gas and theammonia gas may be supplied together with or instead of the depositionmaterial gas for carbon film deposition before completion of thedeposition (typically, immediately before completion of the deposition)while continuing application of the power, so that a carbon nitridelayer may be formed at the surface portion of the carbon film.

In the case where a different kind of gas such as a hydrogen gas is usedas the deposition material gas for carbon film deposition, the gascontaining nitrogen (N) may be supplied instead of the depositionmaterial gas, in which case only supply of the carbon compound gas maybe stopped, and the different kind of gas may be continuously supplied,which is allowed depending on the kind of the gas.

Since the carbon nitride has an extremely high hardness, the depositedcarbon film can have an improved hardness. Since both the nitride layerand the carbon film under the same contains carbon, they have goodadjustment properties and therefore a good adherence.

The material of the deposition target substrate, i.e., deposition targetobject, on which the carbon film is deposited according to the methodand apparatus of the invention, is not restricted, but may be an organicmaterial. The organic material may be thermosetting resin, thermoplasticresin, rubber, paper, wood or the like. In the case where a hard carbonfilm is deposited on the object made of such a material, theconventional plasma CVD method cannot provide a sufficiently good filmadherence, and partial peeling may occur. However, a sufficiently goodfilm adherence can be obtained according to the method and apparatus ofthe invention.

The thermosetting resin may be phenol-formaldehyde resin, urea resin,melamine-formaldehyde resin, epoxy resin, furan resin, xylene resin,unsaturated polyester resin, silicone resin, diallyl phthalate resin orthe like.

The thermoplastic resin may be vinyl resin (polyvinyl chloride,polyvinyl dichloride, polyvinyl butyrate, polyvinyl alcohol, polyvinylacetate, polyvinyl formal or the like), polyvinylidene chloride,chlorinated polyether, polyester resin (polystyrene, styreneacrylonitrile copolymer or the like), ABS, polyethylene, polypropylene,polyacetal, acrylic resin (poly methyl methacrylate, denatured acrylicor the like), polyamide resin (nylon 6, 66, 610, 11 or the like),cellulosic resin (ethyl cellulose, acetyl cellulose, propyl cellulose,cellulose acetate butyrate, cellulose nitrate or the like),polycarbonate, phenoxy resin, fluorocarbon resin (trifluoro chloroethane, ethylene tetrachloride, ethylene tetrachloride propylenehexafluoride, vinylidene fluoride or the like), or polyurethane or thelike.

The rubber may be natural rubber, butyl rubber, ethylene-propylenerubber, chloroprene rubber, chlorinated polyethylene rubber,epichlorohydrin rubber, acrylic rubber, nitrile rubber, urethane rubber,silicone rubber, fluororubber or the like.

The thermosetting resin may be used as a material of films, phonographrecords, various kinds of nets, buttons, ornaments, toys, stationery,and sporting goods, and may also be used as a material of householdarticles such as kitchenwares, various kinds of containers, tableware.It may further be used as a material of electric parts such asinsulators or terminals, or machine parts such as fuel tanks, automobilebodies, automobile bumpers or bearings.

The thermoplastic resin may be used as a material of films, phonographrecords, various kinds of nets, buttons, ornaments, toys, stationery,sporting goods, and may be used as a material of household articles suchas kitchenwares, various kinds of containers or tableware. It mayfurther be used as a construction material, e.g., for water pipings,building members or floor members, or a material of optical parts suchas lenses or prisms, automobile parts such as sealings or packings, ormachine parts such as shock absorbers, gears or bearings.

The rubber may be a material of wiper blades of automobile windows, ortires, sealings or the like of automobiles, bicycles or the like.

Objects made of such resin or rubber may be generally used at portionscausing a friction with respect to other objects coated with lubricantoil for improving a lubricity. However, the amount of lubricant andtherefore the lubricity at these portions decrease with time. The methodand apparatus of the invention may be used to form the carbon film, andtypically the DLC. film having a good lubricity at these frictionportions, whereby low friction properties can be maintained for a longtime. If the method and apparatus of the invention are employed forobjects made of, e.g., resin having a low heat resistance, the heatresistance can be improved.

In addition to the materials described above, ceramics may be thematerial of the deposition target object for carbon film depositionaccording to the method and apparatus of the invention.

In the case where the carbon film is formed on the deposition targetobject made of an organic material by the method and apparatus of theinvention, such pretreatment gas supply means may be employed that cansupply, as a pretreatment plasma material gas for the deposition targetobject, at least one kind of gas selected from a group including, e.g.,a fluorine (F) -contained gas, a hydrogen gas and an oxygen (O₂) gas. Inthis case, the carbon film is deposited on the object after exposing theobject to the plasma of the pretreatment gas.

The above fluorine-contained gas may be a fluorine (F₂) gas, a nitrogentrifluoride (NF₃) gas, a sulfur hexafluoride (SF₆) gas, a carbontetrachloride (CF₄) gas, a silicon tetrachloride (SiF₄) gas, a disiliconhexafluoride (Si₂F₆) gas, a chlorine trifluoride (ClF₃) gas, a hydrogenfluoride (HF) gas or the like.

By exposing the deposition target object to the plasma of the above gas,the surface of the object is cleaned, and the roughness of the objectsurface is improved. These contribute to improvement of the carbon filmadherence.

When employing the plasma of the fluorine-contained gas, fluorinetermination is formed at the object surface. When employing the plasmaof the hydrogen gas, hydrogen termination is formed at the objectsurface. Since fluorine-carbon coupling and hydrogen-carbon coupling arestable, the above termination treatment can provide stable coupling ofcarbon atoms in the film with fluorine atoms or hydrogen atoms in theobject surface portion. Owing to this fact, it is possible to improvethe adherence between the object and the carbon film to be depositedsubsequently. When employing the oxygen gas plasma, contaminants such asorganic matters sticking onto the object surface can be particularlyefficiently removed, which can improve the adherence between the objectand the carbon film to be deposited later.

According to the invention, the pretreatment of the deposition targetobject by the plasma prior to the carbon film deposition may beperformed several times with the same kind of plasma or different kindsof plasma. For example, after exposing the deposition target object tothe oxygen gas plasma, it may be exposed to the fluorine-contained gasplasma or hydrogen-contained gas plasma, and then the carbon film may bedeposited thereon, in which case, after the object surface is cleaned,the fluorine or hydrogen termination is formed at the object surface, sothat the carbon film deposited thereafter has a very good adherence tothe object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic structure of an example of a plasma CVDapparatus according to the invention;

FIG. 2 shows a schematic structure of another example of a plasma CVDapparatus according to the invention;

FIG. 3 shows a schematic structure of still another example of a plasmaCVD apparatus according to the invention;

FIG. 4 shows a schematic structure of yet another example of a plasmaCVD apparatus according to the invention;

FIG. 5 shows a schematic structure of still another example of a plasmaCVD apparatus according to the invention;

FIG. 6 shows a schematic structure of a further example of a plasma CVDapparatus according to the invention;

FIG. 7 shows a schematic structure of further another example of aplasma CVD apparatus according to the invention;

FIG. 8 shows a schematic structure of an example of a plasma CVDapparatus in the prior art;

FIG. 9 shows a schematic structure of another example of a plasma CVDapparatus in the prior art;

FIG. 10 shows a schematic structure of still another example of a plasmaCVD apparatus in the prior art; and

FIG. 11 shows a schematic structure of yet another example of a plasmaCVD apparatus in the prior art;

PREFERRED EMBODIMENTS FOR IMPLEMENTING THE INVENTION

Embodiments of the invention will be described below with reference tothe drawings.

FIG. 1 shows a schematic structure of an example of a plasma CVDapparatus according to the invention. This apparatus differs from theapparatus in FIG. 10 in that a DC power source 6 is connected to theelectrode 2 also serving as an object holder in parallel with a seriescircuit formed of the matching box 31 and the RF power source 32.Structures other than the above are the same as those in the apparatusin FIG. 10, and the same or similar portions bear the same referencenumbers.

For implementing the method of the invention with this apparatus, thedeposition target object S is transported into the vacuum container 1 byan unillustrated object transporting device, and is mounted on theelectrode 2. The exhaust device 5 operates to achieve a predetermineddegree of vacuum in the container 1, and the gas supply unit 4 suppliesthe deposition material gas into the container 1. The electrode 2 issupplied with an RF power from the RF power source 32 through thematching box 31 and is also supplied with a DC. power (usually negative)from the power source 6. Thereby, the plasma is produced from theintroduced deposition material gas, and a predetermined film isdeposited on the object S in the plasma thus produced.

According to the plasma CVD method and apparatus described above, theelectrode 2 also serving as the object holder is supplied with the DC.power for forming a plasma from the deposition material gas, so thationized particles in the plasma are accelerated toward the object Sduring the deposition. Therefore, it is possible to deposit the filmhaving a good adherence to the object S.

FIG. 2 shows a schematic structure of another example of a plasma CVDapparatus according to the invention. This apparatus differs from theapparatus shown in FIG. 11 in that the electrode 2 also serving as anobject holder is not grounded, but is connected to the DC. power source6. Structures other than the above are the same as those in theapparatus in FIG. 11, and the same or similar portions bear D2 the samereference numbers.

For implementing the method of the invention with this apparatus, theelectrode 3 is supplied with a pulse-modulated RF power prepared fromthe RF power generating device 33 through the matching box 31, andsimultaneously the electrode 2 is supplied with a DC. power (usuallynegative) from the power source 6. In this manner, a plasma is formedfrom the material gas.

The pulse-modulated RF power applied to the electrode 3 may be preparedin such a manner that the pulse modulation is effected on the basic RFpower of a frequency from 10 MHz to 100 MHz (e.g., of 13.56 MHz) withthe modulation frequency from 100 Hz to 10 MHz (e.g., from 1 kHz to 100kHz). The duty ratio (on-time/(on-time+off-time)) is determined in arange from 10% to 90%. Deposition operations and conditions other thanthe above are the same as those in the deposition by the apparatus inFIG. 11.

According to the plasma CVD method and apparatus described above, thepulse-modulated RF power is applied to the electrode 3 opposed to theelectrode 2 also serving as the object holder, and simultaneously theDC. power is applied to the electrode 2 serving as the object holder, sothat a plasma is formed from the deposition material gas. As a result,the plasma can have a higher density than that by the conventionalmethod and apparatus, in which a steady or pulse-modulated RF power isapplied, or a steady or pulse-form DC. power is applied for forming aplasma from the material gas. Therefore, a heating temperature of theobject S which is heated by the heater 21 through the electrode 2 can below. Also, ionized particles in the plasma are accelerated toward theobject S during the deposition, so that the film can have a goodadherence to the object S.

FIG. 3 shows a schematic structure of still another example of a plasmaCVD apparatus according to the invention. This apparatus differs fromthe apparatus shown in FIG. 9 in that the RF power generating device 33is employed instead of the RF power source 32, and is connected to thecoil electrode 7 through the matching box 31. The RF power generatingdevice 33 includes the RF power amplifier 34 and the RF arbitrarywaveform generating device 35 connected thereto. The electrode 2 alsoserving as the object holder is not grounded, but is connected to theDC. power source 6. Structures other than the above are the same asthose in the apparatus in FIG. 9, and the same or similar portions bearthe same reference numbers.

For implementing the method of the invention with this apparatus, thepulse-modulated RF power is applied to the induction coil electrode 7,and simultaneously the DC. power (usually negative) is applied to theelectrode 2 for forming a plasma from the material gas. Depositionoperations other than the above are similar to those by the apparatus inFIG. 9.

Deposition by this apparatus can achieve an effect similar to that bythe apparatus in FIG. 2.

FIG. 4 shows a schematic structure of yet another example of a plasmaCVD apparatus according to the invention. This apparatus differs fromthe conventional apparatus shown in FIG. 10 in that the RF powergenerating device 33 is employed instead of the RF power source 32, andis connected through the matching box 31 to the electrode 2 also servingas the object holder. In addition to this, the DC. power source 6 isconnected in parallel with the matching box 31 and the device 33.Structures other than the above are the same as those in the apparatusin FIG. 10, and the same or similar portions bear the same referencenumbers.

For implementing the method of the invention with this apparatus,formation of the plasma from the deposition material gas is performed byapplying the DC. power to the electrode 2 also serving as the objectholder from the power source 6 and by applying simultaneously thepulse-modulated RF power from the RF power generating device 33, andthus is performed by applying both the powers in a superposed manner.Deposition operations other than the above are similar to those by theapparatus in FIG. 10.

According to the above manner and structure, ionized particles in theplasma are accelerated further strongly toward the object S, so that thedeposited film can have a further improved adherence.

FIG. 5 shows a schematic structure of still another example of a plasmaCVD apparatus according to the invention. This apparatus differs fromthe apparatus shown in FIG. 11 in that the electrode 3 is grounded.Further, the matching box 31, an RF power source 340 and an arbitrarywaveform forming device 350 are connected in series to the electrode 2also serving as the object holder, and a circuit formed of a low-passfilter F and a DC. power source 60 is connected in parallel with thisseries circuit. Filter F prevents flow of an RF current to the DC. powersource 60. Structures other than the above are the same as those in theapparatus in FIG. 11, and the same or similar portions bear the samereference numbers.

The DC. power sources 6 used in the apparatuses in FIGS. 1 and 4 alsoemploy low-pass filters similar to the above.

In the apparatus shown in FIG. 5, the pulse-modulated RF power and theDC. power are applied in a superposed manner to the electrode 2,similarly to the foregoing apparatus. The deposition operation andeffect of this apparatus are similar to those of the apparatus in FIG.4.

FIG. 6 shows a schematic structure of a further example of a plasma CVDapparatus according to the invention. This apparatus differs from theapparatus in FIG. 5 in that a pretreatment gas supply unit 8 isconnected to the vacuum container 1 to which the deposition material gassupply unit 4 is also connected. The gas supply unit 8 can supply one ormore of a fluorine-contained gas, a hydrogen gas and an oxygen gas, andis formed of one or more gas sources 831, 832, . . . of the pretreatmentgases connected through mass-flow controllers 811, 812, . . . and valves821, 822, . . . , respectively. Structures other than the above are thesame as those in the apparatus in FIG. 5, and the same or similarportions bear the same reference numbers.

For implementing the method of the invention with this apparatus, theobject S is carried by the electrode 2, and the exhaust device 5operates to attain a predetermined degree of vacuum in the container 1.Then, as a pretreatment gas, one or more kinds of gases selected fromthe fluorine-contained gas, hydrogen gas and oxygen gas are introducedfrom the pretreatment gas supply 8 into the container 1, and the RFpower is supplied to the electrode 2, whereby a plasma is formed fromthe introduced pretreatment gas, and the surface treatment is effectedon the object S under the plasma. Formation of the plasma from thepretreatment gas, which is performed by application of the modulated RFpower in the above manner, may be performed by application of the steadyRF power.

Then, similarly to the deposition by the apparatus shown in FIG. 5, thedeposition material gas is introduced from the gas supply unit 4 intothe container 1, and the plasma is formed from the deposition materialgas by applying the pulse-modulated RF power and the DC. power in asuperposed manner to the electrode 2. Thereby, a predetermined film isformed on the object S.

According to the CVD method and apparatus described above, if the objectS is made of an organic material, the surface of the object S may beexposed to one or more of the fluorine-contained gas plasma, hydrogengas plasma and oxygen gas plasma prior to the deposition. Thereby, thesurface of the object S is cleaned, and the surface roughness of theobject S is improved. Further, if the fluorine-contained gas plasmaand/or hydrogen gas plasma are employed, fluorine termination and/orhydrogen termination are effected at the surface of the object S. If theoxygen gas plasma is employed, contaminants such as organic matterssticking onto the surface of the object S can be removed particularlyefficiently. Therefore, the deposited film (particularly, carbon film)can have a further improved adherence to the object S.

FIG. 7 shows a schematic structure of further another example of aplasma CVD apparatus according to the invention. This apparatus differsfrom the apparatus shown in FIG. 2 in that the DC. power source 6 isreplaced with a DC. power source device 61 allowing turn-on/off of thepower. Structures other than the above are the same as those in theapparatus in FIG. 2, and the same or similar portions bear the samereference numbers.

For implementing the method of the invention with the this apparatus, aplasma is formed from the deposition material gas by applying thepulse-modulated RF power to the electrode 3 opposed to the electrode 2also serving as the object holder and by simultaneously applying the DC.power in the pulse form to the electrode 2 also serving as the objectholder. The pulse frequency of the DC. power in the pulse form is in arange from 1 kHz to 100 kHz, and the duty ratio is in a range from 10 to90%.

Thereby, the plasma thus obtained can have a higher density than that bythe apparatus in FIG. 2, and therefore the heating temperature of theobject S by the heater 21 can be further reduced. Also, ionizedparticles in the plasma can be accelerated further strongly toward theobject S, and thus the deposited film can have a further improvedadherence to the object S.

Although not shown, the apparatuses in FIG. 1 and FIGS. 3 to 6 mayemploy a DC. power source device allowing turn-on/off of the powerinstead of the DC. power sources 6 and 60. This can further lower theheating temperature of the object S by the heater 21, compared with theapparatuses in FIG. 1 and FIGS. 3 to 6, and the deposited films can havea further improved adherence to the object S.

Although not shown, the apparatuses in FIGS. 1 to 4 and FIG. 7 mayemploy the pretreatment gas supply unit 7. This allows deposition of thefilm having a further improved adherence to the object S compared withthe apparatuses in FIGS. 1 to 4 and FIG. 7, when a carbon film or thelike is to be deposited on the object S made of an organic material.

Specific examples for implementing the method of the invention will bedescribed below.

The following table 1 shows deposition conditions of the specificembodiments (embodiments 1-1 to 1-12) of the method of the invention aswell as the deposition examples (comparative examples 1-1 to 1-9) of theconventional plasma CVD method.

In the following table 1, the embodiments 1-1 to 1-6 relate todeposition of titanium-contained films, and comparative examples 1-1 to1-4 are shown for comparison with these embodiments. Comparativeexamples 1-5 to 1-9 are shown for comparison with the embodiments 1-7 to1-12.

TABLE 1 #A #B #C #D #E #F #G E1-1 2 S/DC M TiC TiCl₄, CH₄, H₂ E1-2 4S/DC + M G TiN TiCl₄, N₂, NH₃, H₂ E1-3 7 P/DC M TiCN TiCl₄, CH₄, N₂, H₂E1-4 *1 P/DC + M G TiC TiCl₄, CH₄, H₂ E1-5 3 S/DC — M TiAlN TiCl₄, Al +HCl—AlCl_(3,) N₂, NH₃, H₂ E1-6 *2 P/DC — M TiCN TiCl₄, CH₄, N₂, NH₃, H₂E1-7 2 S/DC M Al₂O₃ Al + HCl—AlCl₃, CO₂, H₂ E1-8 4 S/DC + M G SiO₂SiCl₄, O₂ E1-9 7 P/DC M SiN SiCl₄, N₂, NH₃ E1-10 *1 P/DC + M G SiCSiCl₄, CH₄, H₂ E1-11 3 S/DC — M DLC CH₄, H₂ E1-12 *2 P/DC — M Al₂O₃ Al +HCl—AlCl₃, CO₂, H₂ Cl-1 S/DC G TiN TiCl₄, N₂, NH₃, H₂ Cl-2 P/DC G TiCNTiCl₄, CH₄, N₂, NH₃, H₂ Cl-3 S/RF G TiAlN TiCl₄, Al + HCl—AlCl₃, N₂,NH₃, H₂ Cl-4 G — M TiC TiCl₄, CH₄, H₂ Cl-5 S/DC G Al₂O₃ Al + HCl—AlCl₃,CO₂, H₂ Cl-6 P/DC G SiO₂ SiCl₄, O₂ Cl-7 S/RF G SiN SiCl₄, N₂, NH₃ Cl-8 G— M SiC SiCl₄, CH₄, H₂ Cl-9 G — M DLC CH₄, H₂ #A: Embodiments orComparative Examples E: Embodiment C: Comparative Example #B: Figuresshowing the used appratus (e.g., “3” represents FIG. 3) #C: Powersapplied to electrode 2 S/DC: steady DC power P/DC: pulse form DC powerS/RF: steady RF power M: modified RF power G: ground #D: Powers appliedto electrode 3 #E: Powers applied to induction coil electrode 7 #F:Kinds of films #G: Deposition material gases *1: Apparatus employingpower source 61 instead of power source 6 in FIG. 4 *2: Apparatusemploying power source 61 instead of power source 6 in FIG. 3

The following table 2 shows the deposition temperature, film hardnessand film adherence of the specific embodiments (embodiments 1-1 to 1-12)of the method of the invention shown in the foregoing table 1 as well asthe DD deposition examples (comparative examples 1-1 to 1-9) of theconventional plasma CVD method. The film hardness was determined inVickers hardness (Hv), and the film adherence was evaluated based oncritical loads measured in a scratching method with a diamondpenetrator.

TABLE 2 Deposition Temp. Film Hardness Film Adherence (° C.) Hv (kg/mm²)(N) E1-1 480 3000 40 E1-2 490 2000 45 E1-3 490 2700 43 E1-4 495 3200 40E1-5 487 2600 45 E1-6 485 2650 47 E1-7 480 1800 30 E1-8 490 1300 35 E1-9490 1900 33 E1-10 495 3100 30 E1-11  60 4500 35 E1-12 485 1750 37 C1-1550 1700 20 C1-2 550 1800 25 C1-3 650 1600 21 C1-4 630 1300 19 C1-5 5501200  9 C1-6 550  950 12 C1-7 650 1500 11 C1-8 630 2200 10 C1-9 100 2600 7 #A: Embodiments or Comparative Examples

Deposition Target Object S: stainless steel (SUS304) Deposition GasPressure: 0.1-1 Torr (selected from the range depending on filmmaterial, etc.) Steady RF Power: frequency = 13.56 MHZ 0.3-1 kW(selected from the range depending on film material, etc.)Pulse-Modulated RF Power Basic RF Power: frequency = 13.56 MHZ 0.3-1 kW(selected from the range depending on film material, etc.)pulse-modulation: frequency = 60 kHz duty ratio = 50% Steady DC Power:−1 kV, maximum current value = 20 A Pulse Form DC power basic DC power:voltage = −1 kV maximum current value = 20 A pulse frequency = 10 kHz,duty ratio = 50%

Aluminum trichloride (AlCl₃) of the deposition material gas is producedby reaction of hydrochloric acid (HCl) with aluminum (Al) chips.

From the foregoing results, it can be understood that the films obtainedby the embodiments 1-1 to 1-12 can have higher film adherence, can bedeposited at lower temperatures and can have higher hardness than thefilm obtained by the comparative examples 1-1 to 1-9.

Description will now be given on other specific embodiments ofdeposition of carbon films by the method and apparatus of the inventionas well as comparative examples not employing the method and apparatusof the invention. All of these embodiments and examples commonly employthe apparatus condition that the electrode 2 has a diameter of 280 mm.

Embodiment 2-1

The apparatus in FIG. 1 was used to form a DLC. film on the object Smade of silicon. The DLC. film was formed of an interface layer incontact with the object S and an upper layer. The interface layer wasdeposited by applying a steady RF power and a DC. power in a superposedmanner to the electrode 2 also serving as the object holder. The upperlayer was deposited by applying only the steady RF power to theelectrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicon size (diameter): 4 inches

RF Power: frequency: 13.56 MHz, 150 W

Self-Bias Voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 5 minutes (interface layer) 55 minutes (upper layer)

Embodiment 2-2

The apparatus in FIG. 5 was used to form a DLC. film on the object Smade of silicon. The DLC. film was formed of an interface layer incontact with the object S and an upper layer. The interface layer wasdeposited by applying a pulse-modulated RF power and a DC. power in asuperposed manner to the electrode 2 also serving as the object holder.The upper layer was deposited by applying only the steady RF power tothe electrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicon size (diameter): 4 inches

RF Power

For Interface Layer: Basic RF power of 13.56 MHz and 150 W waspulse-modulated with modulation frequency of 100 kHz and duty ratio of50%.

For Upper Layer: Steady RF power of 13.56 MHz and 150 W.

Self-Bias Voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 7.5 minutes (interface layer) 55 minutes (upper layer)

Comparative Example 2-1

The apparatus in FIG. 10 was used to form a DLC. film on the object Smade of silicon by applying a steady RF power to the electrode 2. TheDLC. film was deposited under the same conditions as those fordeposition of the upper layers in the foregoing embodiments 2-1 and 2-2.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicon size (diameter): 4 inches

RF Power: 13.56 MHz, 150 W

Self-Bias Voltage: −80 V

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 60 minutes

The film stresses and film adherence strengths of the DLC. filmsdeposited in the embodiments 2-1 and 2-2 as well as the comparativeexample 2-1 were measured. The results are shown in the following table3. Deposition rates in these embodiments and example are also showntherein. The film stresses were measured with a laser-type displacementmeasuring device (manufactured by Flexus Corp., 500), and the adherencestrengths of the films were measured with a microscratch device(manufactured by CSEM Corp., Levetester).

TABLE 3 Film Stress Adherence Strength Deposition Rate (dyne/cm²) (N)(Å/min) E2-1 9.2 × 10⁹ 17 30; 60° E2-2 8.5 × 10⁹ 18 20; 60° C2-1 7.2 ×10⁹ 12 60 *interface layer deposition; upper layer deposition

From the results, it can be found that the DLC. films in the embodiments2-1 and 2-2 deposited with applying the DC bias voltage to the electrode2 also serving as the object holder have considerably large filmadherence strengths compared with the DLC. film in the comparativeexample 2-1 not employing the DC. bias.

Embodiment 2-3

The apparatus in FIG. 1 was used, and a DLC. film was formed on thedeposition target object S made of a silicone resin which is athermosetting resin. The DLC. film was formed of an interface layer andan upper layer. The interface layer was deposited by applying a steadyRF power and a DC. power in a superposed manner to the electrode 2. Theupper layer was deposited by applying only the steady RF power to theelectrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicone resin size: 100 mm×100 mm×5 mm (thickness)

RF Power: 13.56 MHz, 150 W

Self-Bias Voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 2 minutes (for interface layer) 16 minutes (for upperlayer)

Embodiment 2-4

The apparatus in FIG. 5 was used, and a DLC. film was formed on thedeposition target object S made of a silicone resin which is athermosetting resin. The DLC. film was formed of an interface layer andan upper layer. The interface layer was deposited by applying apulse-modulated RF power and a DC power in a superposed manner to theelectrode 2. The upper layer was deposited by applying only the steadyRF power to the electrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicone resin size: 100 mm×100 mm×5 mm (thickness)

RF Power

For Interface Layer: Basic RF power of 13.56 MHz and 150 W waspulse-modulated with modulation frequency of 100 kHz and duty ratio of50%.

For Upper Layer: Steady RF power of 13.56 MHz and 150 W.

Self-Bias Voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 2.5 minutes (interface layer) 16 minutes (upper layer)

Comparative Example 2-2

The apparatus in FIG. 10 was used to form a DLC. film on the depositiontarget object S made of silicone resin, which is a thermosetting resin,by applying a steady RF power to the electrode 2. The DLC. film wasdeposited under the same conditions as those for deposition of the upperlayers in the foregoing embodiments 2-3 and 2-4.

DEPOSITION CONDITIONS Deposition Target Object S material: siliconeresin size: 100 mm×100 mm×5 mm (thickness)

RF Power: 13.56 MHz and 150 W

Self-Bias voltage: −80 V

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 17 minutes

The film stresses and film adherence strengths of the DLC. filmsdeposited in the embodiments 2-3 and 2-4 and the comparative example 2-2were measured. The results are shown in the following table 4.Deposition rates in these embodiments and example are also showntherein. The film stresses were measured with the laser-typedisplacement measuring device already described, and the adherencestrengths of the films were measured with the microscratch devicealready described.

TABLE 4 Film Stress Adherence Strength Deposition Rate (dyne/cm²) (N)(Å/min) E2-3 8.2 × 10⁹ 8 150; 300° E2-4 7.5 × 10⁹ 9 120; 300° C2-2 6.2 ×10⁹ 5 300 *interface layer deposition; upper layer deposition

From the results, it can be found that the DLC. films in the embodiments2-3 and 2-4 deposited by applying the DC. bias voltage to the electrode2 also serving as the object holder have considerably large filmadherence strengths compared with the DLC. film in the comparativeexample 2-2 not employing the DC. bias voltage.

Measurement was made to determine friction coefficients of the objectscoated with the DLC. films which were obtained by the embodiments 2-3and 2-4 and the comparative example 2-2 as well as the object S made ofthe same silicone resin as those of the embodiments and example, whichwas coated with silicone oil, i.e., lubricant (comparative example X),and more specifically the friction coefficients between these objectswith respect to an object made of PTFE (polytetrafluoroethylene) weremeasured. The friction coefficients were measured in such a manner thatthe other object made of PTFE having a tip curvature of R18 was laid onthe object coated with the DLC. film, and a weight of 10 grams was laidon the other object with an acrylic plate therebetween. The frictioncoefficients were also measured after repetitively sliding (1000 timesand 5000 times) the other object made of PTFE with respect to the sameportions of the objects coated with the DLC. films at a speed of 50mm/minute. The results are shown in the following table 5.

TABLE 5 Friction Coefficient Initial 1000 times 5000 times E2-3 0.560.56 0.58 E2-4 0.54 0.55 0.56 C2-2 0.55 0.57 1.50 (peeling) CX 0.54 2.524.50

The following can be understood from the results. The frictioncoefficient of the object of the comparative example X coated withlubricant was deteriorated with increase in number of sliding withrespect to the other object. Conversely, according to each of theobjects coated with the DLC. films in the embodiments 2-3 and 2-4 havingthe interface layers which were deposited employing the superposed DC.bias voltages, deterioration of the friction coefficients was not found.According to the object coated with the DLC. film in the comparativeexample 2-2 which did not employ the DC. bias voltage, the film waspartially peeled off and the friction coefficient was deteriorated whenthe sliding occurred 5000 times.

As described above, the DLC. film made of the interface layer and theupper layer was deposited over the object made of thermosetting resin,and the DC. bias voltage was applied when depositing the interfacelayer. Thereby, the hard DLC film can be deposited with a good adherenceon the object made of a resin, i.e., the softer object than the metalobject. Therefore, it can be found that the object had a durablelubricity.

Embodiment 2-5

The apparatus in FIG. 1 was used to form a DLC. film on the depositiontarget object S made of polytetrafluoroethylene (PTFE) which is athermoplastic resin. The DLC. film was formed of an interface layer incontact with the object S and an upper layer. The interface layer wasdeposited by applying a steady RF power and a DC power in a superposedmanner to the electrode 2. The upper layer was deposited by applyingonly the steady RF power to the electrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: PTFE size: 100 mm×100 mm×5 mm (thickness)

RF Power: 13.56 MHz and 150 W (for interface layer)

Self-Bias Voltage: −80 V

DC. bias Power: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 2 minutes (interface layer) 24 minutes (upper layer)

Embodiment 2-6

The apparatus in FIG. 5 was used to form a DLC. film on the object Smade of PTFE which is a thermoplastic resin. The DLC. film was formed ofan interface layer and an upper layer. The interface layer was depositedby applying a pulse-modulated RF power and a DC. power in a superposedmanner to the electrode 2. The upper layer was deposited by applyingonly the steady DC. power to the electrode 2.

DEPOSITION CONDITIONS Deposition Target Object S

material: PTFE size: 100 mm×100 mm×5 mm (thickness)

RF Power

For Interface Layer: Basic RF power of 13.56 MHz and 150 W waspulse-modulated with modulation frequency of 100 kHz and duty ratio of50%.

For Upper Layer: Steady RF power of 13.56 MHz and 150 W.

Self-Bias voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 2.5 minutes (interface layer) 24 minutes (upper layer)

Comparative Example 2-3

The apparatus in FIG. 10 was used to form a DLC. film on the depositiontarget object S made of PTFE, which is a thermoplastic resin, with aplasma formed from a deposition material gas by applying a steady RFpower. The DLC. film was deposited under the same conditions as thosefor deposition of the upper layers in the foregoing embodiments 2-5 and2-6.

DEPOSITION CONDITIONS Deposition Target Object S

material: PTFE size: 100mm×100 mm×5 mm (thickness)

RF Power: 13.56 MHz and 150 W

Self-Bias Voltage: ×80 V

Deposition Material Gas: CH₄, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time: 25 minutes

For the DLC. films obtained in the embodiments 2-5 and 2-6 and thecomparative example 2-3, the film stresses and film adherence strengthswere measured in the same manner as the foregoing. The results are shownin the following table 6. Deposition rates in these embodiments andexample are also shown.

TABLE 6 Film Stress Adherence Strength Deposition Rate (dyne/cm²) (N)(Å/min) E2-5 9.2 × 10⁹ 7 100: 200° E2-6 8.5 × 10⁹ 8  80; 200° C2-3 7.2 ×10⁹ 3 200 *interface layer deposition; upper layer deposition

The following can be understood from the results. The respective DLC.films in the embodiments 2-5 and 2-6 which were deposited with the DC.bias voltage applied to the electrode also serving as the object holderhave considerably larger adherence strengths than the DLC. film in thecomparative example 2-3 which did not employ the DC. bias voltage.

Then, measurement was performed in the same manner as the above todetermine friction coefficients of the DLC-film coated objects obtainedin the embodiments 2-5 and 2-6 and the comparative example 2-3 as wellas an object S made of PTFE, the same material as the above and wascoated with silicone oil, i.e., lubricant (comparative example Y). Theresults are shown in the following table 7.

TABLE 7 Friction Coefficient Initial 1000 times 5000 times E2-5 0.560.56 0.58 E2-6 0.54 0.55 0.56 C2-3 0.55 0.57 1.30 (peeling) CY 0.66 1.202.00

The following can be understood from the results. The object of thecomparative example Y coated with lubricant exhibited the frictioncoefficient which was deteriorated with increase in number of slidingwith respect to the other object. However, each of the DLC. film coatedobjects of the embodiments 2-5 and 2-6 of the invention, which wereformed with the DC. bias voltage, did not exhibit such deterioration ofthe friction coefficient. According to the DLC. film coated object ofthe comparative example 2-3, which did not employ the DC. bias voltage,the film was partially peeled off and the friction coefficient wasdeteriorated when it slid 5000 times with respect to the other object.

As described above, it can be understood that, similarly to theforegoing case of the object made of the thermosetting resin, the hardDLC. film can be deposited on the object made of a relatively soft resinwith a good adherence, and thereby the object can have a durablelubricity.

Embodiment 2-7

In the DLC. film deposition of the embodiment 2-1 using the apparatusshown in FIG. 1, an ammonia (NH₃) gas was added to the depositionmaterial gas immediately before completion of the deposition, so that acarbon nitride layer was formed at the surface portion of the film.

DEPOSITION CONDITIONS Deposition Target Object S

material: silicon size (diameter): 4 inches

RF Power: 13.56 MHz, 150 W

Self-Bias Voltage: −80 V

DC. Bias Voltage: −350 V (only for interface layer)

Deposition Material Gas

For DLC. film: CH₄, 50 sccm For nitride layer: CH₄, 50 sccm NH₃, 50 sccm

Deposition Pressure: 0.1 Torr

Deposition Temperature: 25° C.

Deposition Time DLC film: 50 minutes (including 5 minutes for interfacelayer) Nitride layer: 10 minutes

The hardness and film adherence strengths of the DLC film coated objectsobtained in the embodiments 2-1 and 2-7 were measured. The results areshown in the following table 8. The film hardness was determined inVickers hardness, and the film adherence strength was measured in thesame manner as the above.

TABLE 8 Vickers hardness Adherence strength (N) E2-7 1300 17 E2-1 110017

It can be understood that the DLC. film having the nitride layer at itssurface has a higher hardness than the DLC. film not having the nitridelayer without deteriorating its film adherence.

Embodiment 2-8

In the process similar to that in the foregoing embodiment 2-5 using theapparatus in FIG. 1, pretreatment was effected on the object S made ofPTFE with a sulfur hexafluoride (SF₆) gas plasma prior to thedeposition. The deposition conditions were the same as those in theembodiment 2-5.

PRETREATMENT CONDITION

Pretreatment Gas: SF₆, 50 sccm

RF power: 13.56 MHz, 200 W

Processing Vacuum: 0.1 Torr

Processing Time: 5 minutes

Then, measurement was made to determine the adherence strength of theDLC. film, which was deposited in the embodiment 2-8 affecting thepretreatment with the sulfur pihexafluoride (SF₆) gas plasma, to theobject S. The results are shown in the following table 9. The table 9also shows the adherence strength of the DLC. film deposited in theembodiment 2-5 to the object S.

TABLE 9 Adherence strength (N) E2-8 9 E2-5 7

From the results, it can be found that the DLC. film in the embodiment2-8 employing the pretreatment has a larger adherence strength than theDLC. film of the embodiment 2-5

INDUSTRIAL APPLICABILITY

The present invention can be applied, for example, to deposition offilms having a high wear resistance on tools and mechanical parts,manufacturing of various kinds of semiconductor devices such as ICs andsensors utilizing semiconductors, manufacturing of various kinds ofthin-film devices or the like used in solar cells and liquid crystaldisplays, and formation of films (e.g., DLC films) having a high wearresistance such as ornaments and diaphragms of loud speakers.

What is claimed is:
 1. A plasma CVD method of forming a film on adeposition target object, the method comprising: supplying a depositionmaterial gas to a deposition chamber comprising a pair of electrodes,one of which carries a deposition target object, wherein said depositionmaterial gas comprises a gas of a carbon compound or a gas of a carboncompound together with a gas of a kind different from said carboncompound gas other than nitrogen or ammonia gas; forming a plasma fromsaid deposition material gas by applying a radio-frequency (RF) powerand a direct current (DC) power, wherein said DC power is applied tosaid electrode carrying said deposition target object; and depositing acarbon film on said deposition target object, wherein immediately beforethe completion of said depositing step, either or both a nitrogen gasand an ammonia gas are injected into said deposition chamber, togetherwith said deposition material gas, with the continued application of thepower, thereby allowing the formation of a carbon nitride plasma whichupon deposition forms a carbon nitride film layer on the surface of thecarbon film.
 2. The plasma CVD method according to claim 1, wherein saidRF power is a modulated RF power.
 3. The plasma CVD method according toclaim 2, wherein said modulated RF power is produced by affecting amodulation on a basic RF power of a predetermined frequency with amodulation frequency in a range from 1/10⁵ to 1/10 of said predeterminedfrequency.
 4. The plasma CVD method according to claim 1, wherein saidRF power is applied to an electrode different from said electrodecarrying said deposition target object.
 5. The plasma CVD methodaccording to claim 1, wherein said RF power and said DC. power areapplied in a superposed manner to said electrode carrying saiddeposition target object.
 6. The plasma CVD method according to claim 1,wherein said DC. power has a pulse form.
 7. The plasma CVD methodaccording to claim 1, wherein said deposition target object is made ofan organic material.
 8. The plasma CVD method according to claim 1,wherein said deposition target object is made of ceramics.
 9. The plasmaCVD method according to claim 1, wherein said carbon film is depositedon said deposition target object after said object is exposed to aplasma of at least one kind of gas selected from the group consisting ofa fluorine-contained gas, a hydrogen gas and an oxygen gas.
 10. A plasmaCVD method of forming a film on a deposition target object, the methodcomprising: supplying a deposition material gas to a deposition chambercomprising a pair of electrodes, one of which carries a depositiontarget object, wherein said deposition material gas comprises a gas of acarbon compound or a gas of a carbon compound together with a gas of akind different from said carbon compound gas other than nitrogen orammonia gas; forming a plasma from said deposition material gas byapplying a radio-frequency (RF) power and a direct current (DC) power,wherein said DC. power is applied to said electrode carrying saiddeposition target object; in a first depositing step, depositing aninterface layer of a carbon film on said deposition target object; andthereafter, in a second continuous depositing step, depositing an upperlayer on said interface layer, wherein immediately before completion ofsaid second depositing step, either or both a nitrogen gas and anammonia gas are injected into said deposition chamber, together withsaid deposition material gas, with the continued application of thepower, thereby allowing the formation of a carbon nitride plasma whichupon deposition forms an upper layer of a carbon nitride film on thesurface of the carbon film.
 11. The plasma CVD method according to claim10, wherein said deposition target object is made of an organicmaterial.
 12. The plasma CVD method according to claim 10, wherein saiddeposition target object is made of ceramics.